ETCHING OF ENAMEL SURFACES: Improvements in etching procedures will be sought which will reduce the loss of mineral. Special emphasis will be placed on procedures for incorporating fluoride into the tooth in the form of fluorapatite. The laboratory phase of this research will be terminated and manuscripts describing the results will be written. TOPICAL FLUORIDATION PROCEDURES: Further studies will be carried out to improve procedures which involve formation of CaHPO4.2H2O in the tooth by a pretreatment, followed by a fluoride solution which converts the CaHPO4.2H2O into fluorapatite. Emphasis will be placed on testing of new modalities of application, particularly single-step procedures. Animal studies will continue, and preliminary clinical studies will be initiated. MECHANISM OF FLUORIDE CARIOSTASIS: The improvement diffusion cell will be used to complete the bench scale study of the dynamics of diffusion. Study of the effects of neutral salts on the composition of the solution within the "caries" compartment will be completed. ROLE OF OCTACALCIUM PHOSPHATE IN TOOTH FORMATION: Radioactive phosphorus will be used in an effort to study the involvement of octacalcium phosphate in enamel mineral formation.